The invention relates to a device for locating objects penetrating into a region of space to be monitored. Such devices are for instance used in driver-less transporting systems to determine whether an obstacle could collide with a transport vehicle, and if so then to stop the vehicle.
Such a device is disclosed in published German Patent Application 4 340 756 in which there is provided a housing with a window which extends over an angle of 180.degree., is positioned obliquely relative to the emitted optical radiation and is provided on the underside with an angled edge region. Arranged along the circumference of the window are light barriers whose radiation passes the window and the edge region thereof in order in this way to detect any pollution. The radiation deflected by the deflecting device at a variable angle is partially reflected upon transmission at the two boundary surfaces of the window. Although inclination of the window does prevent said radiation component from inadvertently falling onto the receiver and causing interference, the effect of such inclination of the boundary surfaces to the incident beam is that its optical effect differs in the two principal cutting planes (meridional plane and sagittal plane), resulting in an astigmatic effect. This leads to a considerable restriction, particularly in the case of thicker walls of the window and high demands placed on the beam guidance. Moreover, radiation scattered or detracted at polluted sites of the optical deflecting device or on body edges present there can pass onto the receiver by deflection at the window.
A further device for locating objects penetrating into a region of space to be monitored is disclosed in published German Patent Application 4 315 077, in which an optical deflecting device which can be rotated about an axis is provided which is composed of two mirrors arranged perpendicular to one another, one mirror, arranged at an angle of 45.degree. to the rotation axis, emitting a beam into a region to be monitored, while the other mirror, arranged perpendicular to the previous one, casts a beam, reflected from the region to be monitored, via a concave mirror onto a receiver arranged at the focal point thereof. If this device is accommodated in a housing provided with a window, the same problems arise as have already been discussed above.
Published German Patent Application 19 530 281 has disclosed a device for optically detecting obstacles from vehicles, which comprises a scanner arranged in a housing, the housing being provided with a cambered front plate for sealing against weather effects in a fashion corresponding to a headlamp front plate.